1. Field of the Invention
This invention is concerned with vortex tubes. More particularly, the present invention relates to a method of snowmaking utilizing a vortex tube which design provides a higher snowmaking efficiency by improving process parameters and by elimination of any freeze up during operation.
2. Description of the Prior Art
It is known to make snow by the air and water jets interaction. The system harnessing this method comprises an air nozzle connected with a source of compressed air and a water nozzle connected with the water pump. Both air and water nozzles are mounted on the tower in a manner when the nozzle's axes, being set up in the plane, compose a sharp angle.
A high velocity air jet discharged from the nozzles hits a high velocity water stream and as a result of the impact frozen particles (nuclears) create. Falling down in a cold ambient air, these small particles grow up and turn into snow.
The snowmaking process is very sensitive to the ambient air conditions. Under relatively high temperature and/or air humidity the falling particles became wet or even melt and turn into rain. Under relatively low ambient air temperature an air nozzle may get plugged with ice--as a result of the water droplets freezing on the chilled nozzle surface.
A vortex tube as a means to create a chilled air jet allows to decrease a snowmaking process vulnerability e.g. to operate efficiently under higher ambient air temperatures and/or higher humidity as well as, by utilizing a vortex tube's internal source of heating, eliminate any freeze up during the system operations.
It is known to use a vortex tube for energy separation when the vortex tube is fed with a compressible fluid under a positive (i.e., above atmospheric) pressure. In a vortex tube, the initial flow is transformed into two separate currents of a different energy (a cold and a hot fraction) leaving the vortex tube under pressure which is less than the inlet pressure, but at a pressure still above atmospheric.
A vortex tube comprises a slender tube with a diaphragm closing one end of the tube provided with a hole in the center of the diaphragm for discharge of the cold fraction, one or more tangential inlet nozzles piercing the tube just inside of the diaphragm, and a controlled hot fraction discharge opening such as a throttle valve or any other restrictive body at the far end or the other end of the slender tube.
For the sake of simplicity in the use of terms, the term "throttle" will be used hereinafter in a broad sense to define a controlled hot fraction discharge opening, a restrictive body or a throttle valve.
Even today, the full theory of the vortex tube, explaining all its features, has not yet been created or established. However, the principal mechanism of the vortex phenomenon can be described in the following manner. An expanding gas after passing the tangential nozzle develops into a high speed rotating body (a vortex). The gas in the vortex is cooled because part of its total energy converts into kinetic energy. An angular velocity in the vortex is low at the periphery zone and very high toward the center zone. Friction between the central and periphery zones reduces all of the gas to the same angular velocity as is in a solid body. This causes the inner layer to slow down and the outer layers to speed up. As a result, the inner layers lose part of their kinetic energy and their total temperature decreases. The periphery layers receive the energy from the internal layers. This energy converts to heat through friction in the "hot" end of the tube.
This mechanism can be applied to any vortex tube's mode of operation, e.g. with a separate cold and hot fraction discharge or with an inlet flow discharge through diaphragm (the throttle is closed) or through a throttle valve (diaphragm opening is closed). However, since for the last two vortex tube's modes, the internal (cold) and the external (hot) vortex layers mix up at the same discharge orifice, an outlet flow temperature in the insulated (adiabatic) vortex tube is equal to the inlet gas temperature.